Sens. Michael Bennet (D) and Jeff Flake (R), two of the Gang of Eight immigration reformers, said Wednesday there's room to amend the immigration reform bill to include some things conservatives want without sacrificing Democratic votes. Other 'gang' members are more worried.

Within the sweeping immigration reform measure now before the Senate, there’s room to add border security measures that conservative lawmakers want without laying waste to the path to citizenship that liberals demand, say Sens. Michael Bennet (D) of Colorado and Jeff Flake (R) of Arizona, two authors of the bill.

“We are open to everybody’s good ideas here, as long as they are consistent with the underlying principles in the legislation,” said Senator Bennet. “I think it’s possible to stick with those principles and expand our vote total.”

Bennet, Senator Flake, and the other “Gang of Eight” senators who drafted the bill hope to win 70 Senate votes for their handiwork – a number that they say will show an abundance of support within the Republican caucus and will get the attention of fellow Republicans in the House.

“We can pass this out with 60, 61, 62,” votes, Senator Flake said, “but that doesn’t do us much good in the House.”

The two senators, speaking at a breakfast sponsored by The Christian Science Monitor on Wednesday, said their optimism extends – cautiously, for Bennet – to a border security amendment offered by Sen. John Cornyn (R) of Texas, which is shaping up to be a key test. It would require a higher hurdle for border security before the path to citizenship can open for the more than 10 million undocumented immigrants already in the US.

Senate majority leader Harry Reid (D) of Nevada has called the Cornyn measure a “poison pill,” saying its mix of high border-security hurdles, unclear metrics for determining success, and tying the whole thing to the pathway to citizenship for people already in the US illegally amounts to "a back-door way to undermine the legislation."

Senator Cornyn’s amendment, introduced Wednesday, would require the US to meet certain conditions before illegal immigrants could pursue permanent residency. They include constant observation of the 2,000-mile southern border (including the use of unmanned aerial vehicles in some form or fashion 24 hours a day, seven days a week) and apprehension of 90 percent of potential border-crossers. It also would mandate nationwide implementation of workplace employment verification software known as E-Verify, as well as biometric identification systems in all the nation’s seaports and international airports.

That matches much of the existing bill, which requires the same rate of apprehensions, uses a similar definition of border surveillance, and carries the same broad implementation of E-Verify. But the language of the current Senate bill is less specific about border surveillance requirements, and it would mandate only that passports be screened, not irises and fingerprints, at airports and seaports.

Senator Flake cautioned that Cornyn’s amendment would need to be changed to draw support from Democrats. Cornyn, he added, has shown good faith in saying that if a version of the amendment is adopted he will vote for the bill – a move that would bring the second-ranking Senate Republican and a tough immigration-reform critic into the "yes" column.

Still, the biometric entry and exit systems that conservatives want, as a way to help track people who overstay their visas, may be a part of the Senate bill that could be stiffened. An estimated 40 percent of the undocumented population entered the US legally but stayed longer than allowed.

Flake said he personally believes that a biometric system like the one Cornyn requests could be installed within the next decade. The Arizonan lauded Cornyn for avoiding one request that many consider unworkable: requiring a biometric entry-exit system at all the nation’s land ports. Flake noted that some 10,000 people pass through the turnstiles of a single Arizona border-crossing during a four-hour morning span, but left unsaid what many immigration advocates have long pointed out: that biometric screening of irises or fingerprints in such a circumstance would be enormously expensive and have huge consequences for trade and travel across the border.

Bennet was less effusive about expanding biometric screening but didn’t knock the idea entirely.

“In the Gang, there was a limit to what we were willing to spend on the biometric system," Bennet said, "and we were already spending a great deal of money on the border.”

Bennet may have been holding his fire, given the derision Cornyn encountered on the Senate floor Wednesday by two others in the Gang of Eight: Sens. Chuck Schumer (D) of New York and John McCain (R) of Arizona. When Cornyn came to the floor to discuss his amendment Wednesday afternoon, Schumer and McCain savaged the Texan for moving too much money into border security personnel at the expense of other priorities, among other complaints.

Chiefly, Bennet and Flake argued that they aren’t afraid of adding a requirement to nab 90 percent of would-be border-crossers, because the bill's $5 billion in new spending on more border security, its mandatory workplace verification, and its sizable guest worker programs would stem the flow of illegal immigrants.

All those provisions, Flake said, would make it possible to “blow through” the 90 percent threshold of nabbing would-be crossers, well before the next decade is out.

“I have every confidence,” Bennet seconded, “that we’re going to meet the mark well before the 10 years.”